add requirements.txt?

[srl295]

Hello,
Would it be helpful to add a requirements.txt next to heatmap.py so that you can run pip install -r requirements.txt to run it? With the following contents:

# pip install -r requirements.txt
image>=1.5.33

[Sn1PeR]

To add to this, the latest version of Pillow removed the getsize method, to fix this:
Pillow==9.5.0